Prior to the present invention, the present inventor designed the retainer device in a manner substantially similar to the present inventive subject matter, except devoid of what has now been developed as a critical component to make the device operate without a substantial problem associated previously. In particular, while the mechanism of releasing an extended dental instrument and attached extended tube thereof from an extended state to thus permit retraction thereof, worked substantially by the same mechanism as the present invention, namely to pull forwardly to a further extended state and flip-upwardly the cord to cause the retainer ring to become instantly raised to a level during concurrent retraction as to ride on top of an overhang structure to a rearwardly direction and thus not be further retained, it was found that much too often when the dentist flipped the cord with a flip of the wrist, that the cord completely left the groove or slot of travel such that retraction pulled the instrument to a position outside of the retaining seat whereby the instrument was not in the retaining seat nor retained at all, but continued rearwardly if the instrument were released by the hand of the dentist or dental assistant. This caused considerable distraction and required time and care to assure that retraction was always proper and complete to an instrument-seated state.